With the rapid development in technological fields, light-emitting diodes (LEDs) have gradually replaced the bulbs and mercury-containing fluorescent tubes as a light source in commercially available illuminating devices. This is because the LED has low power consumption, long service life, no idling time, and fast response speed, and is flicker-free to protect a user against sore eyes. Moreover, the LED is small in size, vibration-proof, easy for mass production, and may be produced into an extremely small size or an array-type element. Therefore, the LED has been widely used as a light source in digitalized 3C products, automobile lamps, and ornamental lamps. It can be seen that the LED has become a main light source in the development of future illuminating field.
While the currently available LED light source has reached a considerably high brightness, there are still some technical problems in the LED that need improvements. The first problem with LED is heat dissipation. Most of the commercially available LED products and patents to the prior art LEDs pay a lot of attention to the heat radiation efficiency of the LED. While some conventional LEDs have good heat dissipation efficiency to avoid being overheated, these conventional LEDs consume more power supply. And, when the LEDs have been used over a long period of time, they are subject to a gradually increased brightness attenuation rate and accordingly shortened the lifespan.
Further, when the LED is used as a light source for an illuminating device, the illuminating device must only be connected to a direct current (DC) power supply. An alternating current (AC) power supply cannot be used with the LED. Therefore, when it is desired to widely use the LED to replace general lighting devices and illuminating products, an AC/DC converter must be provided along with the lighting devices or illuminating products that use LED as a light source thereof. By doing this, it would inevitably bring inconveniences to the users.